The preferred embodiment of the present invention is particularly directed to a cable drive system for moving an ink jet printer along a guide bar for scanning a print medium on which an image is printed. In general terms the underlying invention is directed to a cable drive system for moving a mass along a predetermined path, and is therefore generally applicable to any flexible-element drive system. It will be understood in the following description that although reference is made to the ink jet printer environment, the invention is not limited to this application.
In a cable or timing belt drive for moving a printer head in a back and forth motion along a guide member, one of the important parameters is the stiffness of the drive system. The stiffness (K), along with the mass (M) of the printer head carriage, determines the natural frequency .omega..sub.N of the system to be driven: ##EQU1##
It is usually very desirable to keep .omega..sub.N and thus K as high as possible. This requirement produces a dilemma. To prevent excessive preload changes with environmental shifts, K should be as low as possible.
The usual solution is to provide a spring loaded idler pulley so that the position of the pulley can vary to compensate for changes in the belt or cable length. However, the idler spring combines with the cable or belt stiffness to produce a much lower overall stiffness.
It is therefore desirable to provide a drive system that has high performance without being subject to environmental changes.